The present invention relates in general to detection and display of the fine particulate concentration within the air, and, more specifically, to a method and a device for adjusting fine particulate measurement values detected by means of a sensor for detecting fine particulates within a motor vehicle.
Motor vehicles can be equipped with a built-in sensor for detecting fine particulates that are present in the air, particularly in order to display the fine particulate concentration within the motor vehicle and/or in the environment outside the motor vehicle in real time. A correct estimate of the fine particulate loading or the fine particulate concentration using sensors to measure them presents certain challenges, in particular in connection with sensors that perform optical detection of the fine particulates. Most sensors are calibrated for a specific range of fine particulate concentrations. Within said range, the sensors react differently, for example depending on whether they are fixed measuring or monitoring stations or depending on a certain calibration device being used that is usually designed for high-precision measurement or for laboratory quality measurements.
Sensors for detecting fine particulates are sensitive to variations in certain environmental conditions, in particular temperature, air humidity, and vibration, as well as to variations of the operating conditions of air conditioning systems, such as for example the use of recirculated air or a fresh air feed or the presence of an open or closed window, etc. Any of these conditions can temporarily disturb the concentration of particulates present at the sensor. Taking into account the different possible combinations of such conditions, there is a challenge in developing a control strategy so that the fine particulate loading can be read out as precisely as possible by means of the sensors.
In addition, it is possible that a vehicle occupant directly contributes to a variation of the fine particulate concentration within the vehicle, for example when the occupant smokes (such as smoking conventional cigarettes or E-cigarettes). In this case, the type, size, and concentration of the aerosols sometimes differ from aerosols that result from sources outside the vehicle. In this case, it is not desirable to inform the vehicle occupant about a fine particulate concentration value caused by their own actions, but up to now there are no reliable methods for distinguishing whether the fine particulate has been produced intentionally or not.
In prior patent document U.S. Pat. No. 9,688,194 B2, a method for analyzing fine particulate measurement values by means of fine particulate sensors in connection with motor vehicles is described.